This revised application for a Mentored Research Scientist Development Award (KOl) is from a licensed clinical psychologist and Assistant Professor of Psychiatry. He is proposing a research career development plan that will enable him to learn how to use diffusion tensor imaging and functional magnetic resonance imaging techniques to better elucidate the neurobiology and neuropsychology of obsessive-compulsive disorder (OCD). Compared to other major psychiatric disorders such as schizophrenia and depression there have been fewer neuroimaging studies in OCD, and the majority of studies conducted thus far have utilized either PET or SPECT. Moreover, the neural mechanisms underlying cognitive dysfunction in OCD have been poorly elaborated. The applicant has preliminary data (Szeszko et al 1999) implicating orbital frontal lobe structural abnormalities in OCD using morphometric methods and wants to learn how to conduct additional studies investigating the frontal lobes of these patients. The training plan would increase the applicant's knowledge in three broad domains: (1) neurobiology, phenomenology and pharmacology of OCD; (2) diffusion tensor imaging and (3) neuropsychology of OCD and cognitive neuroscience applications of fMRI in OCD. The training goals will be accomplished through the completion of the research plan, which will examine the relative contributions of dorsal and ventral frontal regions to the pathophysiology of OCD using brain morphometry, diffusion tensor imaging, functional magnetic resonance imaging and comprehensive neuropsychological assessment. In collaboration with the applicant's mentors and consultants various statistical and image processing techniques will be used to analyze and interpret the neuroimaging data and the functional correlates of structural brain pathology will be identified. Completion of the training goals and research studies are expected to provide the applicant with the knowledge and experience to develop into an independent investigator capable of conducting high quality neuroimaging studies in OCD and to apply for an ROl.